Anesthetic induction agents, sympathetic nerve activity and baroreflex sensitivity: a study in rabbits comparing thiopental, propofol and etomidate

The mechanisms of arterial hypotension following intravenous anesthetic induction agents are multifactorial. The purpose of this study was to evaluate and compare the effects of thiopental, propofol and etomidate on hemodynamics, sympathetic outflow and arterial baroreflex sensitivity using not only neuraxis-intact but also totally baro-denervated rabbits. A total of 60 rabbits was anesthetized with urethane, tracheotomized, and mechanically ventilated with oxygen in nitrogen (FiO2 0.5). The left renal sympathetic nerve was isolated and placed on a bipolar electrode to record renal sympathetic nerve activity (RSNA). Thirty animals underwent a surgical preparation of total baroreceptor denervation. Bolus injections of an anesthesia induction dose of thiopental 4 mg/kg and twice the induction dose of propofol 4 mg/kg significantly decreased RSNA to the same extent (19.4+/-6.7 and 19.7+/-5.2% reduction, mean +/- SEM) and mean arterial pressure (MAP) also to the same extent (19.5+/-4.6 and 22.1+/-3.1% reduction) in the neuraxis-intact animals. RSNA was increased (34.5+/-6%) without reduction of MAP by an induction dose of etomidate, 0.3 mg/kg. Sympathetic barosensitivity was attenuated even 10 min after thiopental at 4 mg/kg or propofol at 4 mg/kg (68% and 54% of control, respectively). Propofol at 2 mg/kg (induction dose) and etomidate at 0.6 mg/kg decreased RSNA and MAP only in the baro-denervated animals. It was found from the barosensitivity study that patients can be hemodynamically unstable even though blood pressure has returned to normal after thiopental and propofol administration. Data suggest that etomidate can even stimulate the sympathetic nervous system and increase sympathetic outflow. It was also clearly found from the baro-denervated animal study that thiopental was stronger than propofol in directly suppressing sympathetic outflow at the induction dose.     

Identification of a new locus for autosomal dominant non-syndromic hearing impairment (DFNA7) in a large Norwegian family

Hereditary hearing impairment affects about 1 in 1000 newborns. In most cases hearing loss is non-syndromic with no other clinical features, while in other families deafness is associated with specific clinical abnormalities. Analysis of large families with non-syndromic and syndromic deafness have been used to identify genes or gene locations that cause hearing impairment. The present report describes a large Norwegian family with autosomal dominant non-syndromic, progressive high tone hearing loss with linkage to 1q21-q23. A maximum LOD score of 7.65 (theta = 0.00) was obtained with the microsatellite marker D1S196. Analysis of recombinant individuals maps the deafness gene (DFNA7) to a 22 cM region between D1S104 and D1S466. The region contains several attractive candidate genes. This report supports the idea of extensive genetic heterogeneity in hereditary hearing impairment and represents the first localization of a deafness gene in a Norwegian family.      

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

CLINICO-EPIDEMIOLOGICAL ALGORITHM FOR PREDICTING SYSTEMIC ARTERIAL HYPERTENSION AT HIGH ALTITUDE THROUGH MATHEMATICAL MODELLING

A population based hybrid design combining element of cohort and cross-sectional approach was used to develop a simple clinical algorithm to predict individual probability of developing hypertension (systolic BP > 140 mm Hg and/or diastolic BP > 90 mmHg). 3615 soldiers initially normotensive at the time of induction into high altitude, were studied by systematic random sampling. Multiple logistic regression analysis showed a high significant association between hypertension and age, body mass index (BMI), tobacco smoking and alcohol consumption. Using the constant/coefficient values obtained from the logistic model and the receiver operating characteristics (ROC) curve analysis, the following predictive rule was developed – To the age in years, add (BMIx 3.86); also add 5.53 if he is a smoker; and add 19.81 if he consumes alcohol. If the total exceeds 142, the individual is at high risk of developing hypertension. This algorithm carries a sensitivity of 68.2% and specificity of 78.5%.KEY WORDS: Hypertension, High altitude     

Knowledge about pain among newly graduated occupational therapists: relevance for curriculum development

In recent years there has been a growing awareness amongst health professionals of the need to prepare undergraduate students more adequately for practice with clients who have pain. Occupational therapists have a central role in enabling such clients to have productive lives despite pain. In this study, an examination was made of the adequacy of preparation for pain practice in graduates from one Australian occupational therapy curriculum. Recent occupational therapy graduates from the University of Queensland, Australia, who responded to a postal survey, obtained an overall 53% correct response rate to a 69-item pain knowledge and attitudes questionnaire. Results indicated the need for further education in this area, especially in the areas of pharmacological management, and pain assessment and measurement. These results were comparable to those obtained from final year occupational therapy students at Dalhousie University in Halifax, Nova Scotia prior to undertaking an elective course about pain. Follow-up interviews with a number of new graduates supported the inclusion of an elective pain course in the undergraduate occupational therapy curriculum at the University of Queensland in Australia.     

In vitro reaction of the carcinogen, N-hydroxy-2-naphthylamine, with DNA at the C-8 and N2 atoms of guanine and at the N6 atom of adenine

The probable ultimate urinary bladder carcinogen, N-hydroxy-2-naphthylamine(N-HO-2-NA), reacted with nucleic acids and proteins under mildlyacidic conditions (pH 5) to form covalently bound derivatives.The extent of reaction was in the order: poly-guanylic acid>DNA protein rRNA >tRNA >polyadenylic acid, polyuridylicacid >polycytidylic acid. At pH 7, appreciable reaction occurredonly with protein. Enzymatic hydrolyses of the DNA, which contained1.5 naphthyl residues/1000 nucleotides, yielded 3 nucleoside-arylamineadducts. From chemical, u.v., n.m.r., and mass spectrometricanalyses, the adducts were identified as 1-(deoxy-guanosin-N²-yl)-2-naphthylamine,1-(deoxyadeno-sin-N⁶-yl)-2-naphthylamine, and a purine ring-openedderivative of N-(deoxyguanosin-8-yl)-2-naphthylamine, tentativelyidentified as 1-[5-(2,6-diamino-4-oxopyrimidinyl-N⁶-deoxyriboside)]-3-(2-naphthyl)urea.The properties of these adducts and their possible role in theinitiation of carcinogenesis are discussed.